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Stainless Steel vs Catalytic Corrosion


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Hi Folks,

Came across an article suggesting that stainless steel fittings can encourage catalytic corrosion.

http://funrover.com/guides/8-jobs-you-should-be-doing-to-your-land-rover/

Not heard that before and wondering is that common knowledge/accurate?

The article suggests using Duralac anti corrosive jointing compound or something similar. Again, not heard of this before. Have folk got experience of taking such precautions?

Thanks,

Simon...

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I rebuilt my 90 with a brand-new body back in 2001 and used SS fixings throughout however I always assemble fixings with either Waxoyl or Copperslip (depends on the location), one thing I NEVER do is assemble dry.

My body is now showing signs of corrosion but this is NOT around the fixings but instead along normal locations like the  door bottoms, wheel arches etc (only doors and rear tub however as the front wings & bonnet remain perfect) so I think it is safe to say that the use of SS fixings has had no effect over the past 18-years.

Rear tub is coming off this summer and being stripped & re-painted whereas the doors are being replaced with galvanised ones.

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The tendency to corrode when dissimilar metals are in contact depends on the electrode-potentials of the metals in question. The further-apart they are in the electrochemical-series the greater the 'battery' they generate when wetted and the worse the corrosion will be.

See here: https://www.engineeringtoolbox.com/electrode-potential-d_482.html

When you're dealing with alloys [like stainless, or brass], take the most-extreme electrode-potential as the default. Brass and Aluminium, for example - the Copper in the brass has a potential of +0.34 and Aluminium has a potential of -1.67 meaning they will react like crazy when wet!

Zinc and Aluminium are 'relatively' close-together [-0.76 and -1.67] so they shouldn't corrode too badly.

Aluminium at -1.67 and Iron at -0.44 are further apart, hence the creeping corrosion that sets in between the un-galvanized body-cappings and the aluminium body-panels on Defenders.

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"one thing I NEVER do is assemble dry." - Yep. Generally use copper grease.

Makes me wondering whether should be using galvanised bolts when doing replacements. Need to put in two new front seat belts and was considering new bolts for the brackets which mount the end of the belts to the floor pan.

Simon...

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Stainless fasteners are awful in other ways too - they are brittle and absolutely love to gall and lock solid if you get any crud in the threads, and of course they're hard so harder to drill out than a BZP one.

I use BZP all the way - I usually buy party packs from Namrick, Cromwell, or Axminster.

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